With the tendency of high resolution and high yield of OLED manufacturing, the requirement for deposition accuracy is increasingly higher. Therefore, it is essentially important to measure the deposition offset and compensate for the offset accurately and quickly for meeting the above requirement.
FIG. 1 and FIG. 2 respectively illustrate a front view and a top view of OLED sub-pixels deposition by using a deposition equipment. The deposition equipment includes an evaporation source 1, a metal frame 2, a mask 3 and a glass substrate 4. The mask 3 is, for example, a fine metal mask (FMM), having a hollow portion 31 therein and fixed on the metal frame 2. Before evaporation, the glass substrate 4 and the mask 3 are set opposite in position, i.e., a predetermined position of a light emitting unit 41 on the glass substrate 4 is set to correspond to the hollow portion 31. The evaporation source 1 containing an OLED material is then evaporated to make the OLED material deposit on the light emitting unit 41 of the glass substrate 4 via the hollow portion 31 on the mask 3, forming RGB sub-pixels P, as shown in FIG. 3 and FIG. 4. Next, in the same manner, a multilayer structure is stacked and formed on the glass substrate 4 using masks in other layouts, so as to form three layers of sub-pixels respectively. After the OLED manufacturing process is completely finished, the glass substrate 4 is powered on to be lit up. Whether there exists an offset between the light emitting unit 41 and the deposited sub-pixel of the OLED material is observed after the glass substrate 4 is powered on, and the offset is measured.
Next, the offset is compensated by moving the glass substrate 4 or the mask 3, so as to avoid a reoccurrence of the offset.
However, the above offset measuring step can be carried out only when the glass substrate 4 is powered on after the OLED manufacturing process is completely finished. Therefore, even if the offset is detected and compensated, the deposition layer with the offset has severely affected the subsequent manufacturing process in fact. The defective substrates produced in large quantity cannot be compensated, and therefore cannot be used.
Therefore, the existing offset measurement method can discover and measure the offset only after the manufacturing process is completed, which results in a lower manufacturing efficiency, a waste of raw materials, and a higher defective index.
Therefore, there needs a method for measuring an offset of the sub-pixel on the OLED substrate, so as to discover the deposition offset earlier, improve the manufacturing efficiency and increase the product yield.
The above information disclosed in the background section is only for enhancing the understanding of background of the present disclosure, therefore it may include the information which does not constitute the prior art known to those skilled in the art.